Sorry to dig up an old thread. Its the one that I kept coming to for information, so I figured I would add my experience.
For me the left (driver) side adjuster was at 3 o'clock. Also I didn't really know what to expect with the adjuster. I expected a screw. I ended up having to take off the caliper and rotor to take a peek. I attached the picture I took for anyone who is as confused as I was. The picture is the left (driver) side rear. The gray cylindrical thing next to the spring is the adjuster.
I don't think you can see the adjuster very well through the lug hole. I couldn't see it. I think you just have to know that its next to the spring and know how to adjust it. Then the rest is kind of feeling around with the screw driver.
I also found this video where a mechanic shows how to adjust a Porsche parking brake. It looks similar and shows the operation of the adjuster.
YouTube - DIY - changing rear brakes (and adjusting parking brake) on a water-cooled Porsche